以外腔式可调谐、 窄线宽近红外半导体激光为光源, 以一对曲率半径r=1 000 mm的宽带高反射率平凹镜(反射率R=99.97%)构成的腔长为650 mm的对称高精度光学稳定腔, 建立了腔增强吸收光谱系统。详细研究了纯净N2O气体、 以及N2O和N2的混合气体在不同浓度和不同气压下、 中心波长位于6 561.39 cm-1的腔增强吸收光谱、 光谱强度和谱线宽度, 该腔增强吸收光谱系统的有效吸收光程可达1 460 km。获得了光谱线宽与气体压强的关系曲线, 导出了波数6 561.39 cm-1处N2对N2O的压力展宽系数为(0.114±0.004)cm-1·atm-1。采用该腔增强吸收光谱系统, 开展了N2O气体检测研究, 建立可用于定量检测的N2O气体腔增强吸收光谱强度与气体浓度关系曲线, 获得了2.34×10-7cm-1的检测灵敏度, 多次重复测量的相对标准偏差(RSD)为1.73%, 在微量N2O气体检测中具有很好的应用前景。

Using a tunable near infrared external cavity diode laser and a 650mm long high finesse optical cavity consisting of two highly reflective (R＝99.97% at 6 561.39 cm-1) plan-concave mirrors of curvature radius ~1 000 mm, a cavity enhanced absorption spectroscopy (CEAS) system was made. The absorption spectra centered at 6 561.39 cm-1 of pure N2O gas and gas mixtures of N2O and N2 were recorded. According to the absorption of N2O at 6 561.39 cm-1 in the cavity, the measured effective absorption path was about 1 460 km. The spectra line intensity and line-width of N2O centered at 6 561.39 cm-1 were carefully studied. The relationship between the line-width of absorption spectra and the gas pressure was derived. The pressure broadening parameter of N2 gas for N2O line centered at 6 561.39 cm-1 was deduced and given a value of ~(0.114±0.004) cm-1·atm-1. The possibility to detect trace N2O gas in mixture using this CEAS system was investigated. By recording the absorption spectra of N2O gas mixtures at different concentration, the relationship between the line intensity and gas concentration was derived. The minimum detectable absorption was found to be 2.34×10-7 cm-1 using this cavity enhanced absorption spectroscopy system. And te measurement precision in terms of relative standard deviation (RSD) for N2O is ~1.73%, indicating the possibility of using the cavity enhanced absorption spectroscopy system for micro gas N2O analysis in the future.